There is no such thing as "creating value" out of gifts. You need to be honest with yourself. With each gift/freebie, you need to say to yourself what it's really worth TO YOU -- that is, how much you would pay for the same thing in real money (NOT how much it would have costed, as that's irrelevant).
For example, when I get Shell gas cards from CET (either Great Gift Wrap Up or other promos), they are worth close to face value to me, but not 100%. I always need to buy gas, so these honestly save me real $ I would have spent, but they are a bit inconvenient in that I have to use them at Shell, which either might be more expensive or farther away than I'd prefer to go. I'd say I would personally value Shell cards at 95% of the face value.
Freeplay I value at around 99% of the face value, since that's the average takeaway on an 8/5 bonus machine. Unlike Alan, I am not results-oriented per session of freeplay. It will roughly average out in the long run.
Other things are harder to value. Free hotel rooms are worth something, but sometimes I use them just because they're a benefit, but I otherwise wouldn't have traveled without them. So I don't know what they're worth. They are worth something to me during the World Series of Poker. I basically spent a month at the Rio for free during the 2013 WSOP.
Free food I value at the non-inflated prices, and only if I enjoy it. So if I eat a $70 steak at Old Homestead at Caesar's, I know that it's really worth more like $45.
In 2013 I combined my Seven Stars annual trip to New Orleans with a cruise out of the same location, and I did it during the Christmas/New Years high season. The "value" of the cruise was about $3000 and the flight was $1200, but I wouldn't have spent $3000 on a cruise at that time of year if I was spending my own money (prices were inflated due to the season). I also got $500 in RCs for taking the trip (you get that instead of that obnoxious food credit at Harrah's New Orleans, which is great).
Anyway, I do enjoy the Seven Stars perks and the offers, but I never put unrealistic values on them.